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Biomedical subjects

T Ren

Publications and source records attributed to T Ren.

At least 37 records · Page 2Linked to original sources
PubMed2000

HRT gene function requires interaction between a NAC protein and viral capsid protein to confer resistance to turnip crinkle virus.

An Arabidopsis protein was found to interact specifically with the capsid protein (CP) of turnip crinkle virus (TCV) through yeast two-hybrid screening. This protein, designated TIP (for TCV-interacting protein), was found to be a member of the recently recognized NAC family of proteins. NAC proteins have been implicated in the regulation of development of plant embryos and flowers. TIP alone was able to activate expression of reporter genes in yeast if fused to a DNA binding domain, suggesting that it may be a transcriptional activator. The TIP binding region in the TCV CP has been mapped to the N-terminal 25 amino acids. Site-directed mutagenesis within this region revealed that loss of the TIP-CP interaction in the yeast two-hybrid assay correlated with loss of the ability of TCV to induce the hypersensitive response and resistance in the TCV-resistant Arabidopsis ecotype Dijon (Di-0 and its inbred line Di-17). These data suggest that TIP is an essential component in the TCV resistance response pathway.

Amino Acid Sequence↗
PubMed2000

Production and consumption of nitric oxide by three methanotrophic bacteria.

We studied nitrogen oxide production and consumption by methanotrophs Methylobacter luteus (group I), Methylosinus trichosporium OB3b (group II), and an isolate from a hardwood swamp soil, here identified by 16S ribosomal DNA sequencing as Methylobacter sp. strain T20 (group I). All could consume nitric oxide (nitrogen monoxide, NO), and produce small amounts of nitrous oxide (N(2)O). Only Methylobacter strain T20 produced large amounts of NO (>250 parts per million by volume [ppmv] in the headspace) at specific activities of up to 2.0 x 10(-17) mol of NO cell(-1) day(-1), mostly after a culture became O(2) limited. Production of NO by strain T20 occurred mostly in nitrate-containing medium under anaerobic or nearly anaerobic conditions, was inhibited by chlorate, tungstate, and O(2), and required CH(4). Denitrification (methanol-supported N(2)O production from nitrate in the presence of acetylene) could not be detected and thus did not appear to be involved in the production of NO. Furthermore, cd(1) and Cu nitrite reductases, NO reductase, and N(2)O reductase could not be detected by PCR amplification of the nirS, nirK, norB, and nosZ genes, respectively. M. luteus and M. trichosporium produced some NO in ammonium-containing medium under aerobic conditions, likely as a result of methanotrophic nitrification and chemical decomposition of nitrite. For Methylobacter strain T20, arginine did not stimulate NO production under aerobiosis, suggesting that NO synthase was not involved. We conclude that strain T20 causes assimilatory reduction of nitrate to nitrite, which then decomposes chemically to NO. The production of NO by methanotrophs such as Methylobacter strain T20 could be of ecological significance in habitats near aerobic-anaerobic interfaces where fluctuating O(2) and nitrate availability occur.

Genes, rRNA↗
PubMed2000

[Periodontal regeneration by application of the porous beta-TCP/BMP artificial bone to Class II furcation defects].

OBJECTIVE: To study the regeneration of periodontal tissue after the application of beta-TCP/BMP artificial bone to class II furcation defects. METHODS: Periodontal defects were produced surgically around premolar teeth in 4 dogs. The flap surgery was performed and the root surfaces were curetted to remove the periodontal ligament and the cementum. A synthetic bioabsorble barrier manufactured from poly DL-lactide was used. The defects were divided into 3 groups (beta-TCP/BMP + PDLLA, PDLLA, control). 12 weeks after surgery, the animals were sacrificed and the teeth with their supporting periodontium were processed for light microscopic evaluation. RESULTS: The definitive evidences of regeneration were founded both in BMP/GTR group and GTR group, but the BMP/GTR group exhibited more new bone formation, cementum deposition occupying the majority of the furcation defects than the other two groups. CONCLUSION: It was concluded that the beta-TCP/BMP artificial bone can be used in GTR technique to promote periodontal regeneration.

Animals↗
PubMed2000

[Epidemiological studies on the relationship between body weight and the prevalence rate of impaired glucose tolerance (IGT) in the population of urban areas of Tianjin city].

OBJECTIVE: In order to explore the relationship between body weight and the prevalence rate of IGT in a community - based population and to provide scientific informations of IGT for prevention and control. METHODS: Cluster sampling was carried out in prevalence survey, together with clinical examination and test of blood plasma glucose. RESULTS: A sample of 62,577 people was performed by cluster random sampling. Results showed that the crude prevalence rate of IGT in the whole population of three communities was 13.13 per thousand in males, 19.18 per thousand in females, and 16.23 per thousand in both sexes respectively. The IGT prevalence rate of different body weight group in community population had a marked difference. There was a trand that the IGT prevalence rate increased markedly with the increase of body weight. CONCLUSION: The incidence of IGT is related to body weight and obesity.

Adolescent↗
PubMed1999

Synthesis of diether-linked cationic lipids for gene delivery.

Quaternary ammonium lipids 1b-d, with diether linkages between hydrocarbon chains and butane or hexane backbone, were synthesized for cationic liposome-mediated gene delivery. The synthetic strategy of using C-4 or C-6 synthon permits the achievement of the variation of the hydrophobic domain as well as changes of space between the quaternary ammonium head and the hydrophobic domain in the diether-linked cationic lipids.

Genetic Therapy↗
PubMed1999

[Effect of low dose gamma-irradiation and cigarette smoking on growth and reflex behavior in mice].

Pregnant mice were exposed to different level of gamma-irradiation(60Co 0, 0.25, 0.5 and 1.0 Gy) and water solutions containing different contents of substance from cigarette smoke(0, 0.5, 1.0, 1.5 and 2.0 cigarette/mouse). Results showed that the effect of low dose gamma-irradiation and high concentration cigarette smoke substance could delay the appearance of four physiological markers (eye opening, pinna detachment, hair growth and tooth growth) and the acquisition of four reflexes(surface righting, air righting, virual placing and auditory orienting). A significant combined effect was also observed.

Animals↗
PubMed1999

The radial pattern of basilar membrane motion evoked by electric stimulation of the cochlea.

Electric current applied to the cochlea can evoke in situ electromotile responses of the organ of Corti. These nonsound-generated responses can give insight into the mechanics of the organ as the putative forces produced by outer hair cells (OHC) must couple to the modes of vibration of the basilar membrane (BM). In this study, platinum-iridium wire electrodes were positioned into the scala vestibuli and scala tympani of the first cochlear turn in the guinea pig. Current (1.5 ms rectangular-shaped pulses) was applied to these electrodes at levels to 500 microA peak. A laser Doppler velocimeter was used to record the velocity or displacement of the basilar membrane at the tonotopic 18 kHz place via an opening into the scala tympani of the first cochlear turn. Beads were positioned across the width of the BM so that the velocity or displacement of the BM could be studied in the radial direction. It was found that the current pulses evoked linear displacements of up to 2 nm for current levels of 500 microA (higher levels were damaging to the organ of Corti). The pattern of motion across the width of the BM was such that maximum displacement and velocity was located near the first row of OHCs and the position of the outer pillar cell footplate. The BM motion was biphasic in that the zona arcuata moved in the opposite direction to that of the zona pectinata. The results of this study demonstrate that the level of force produced by OHCs is effective in moving the BM and that the distribution of force within the organ of Corti leads to a multimodal motion pattern of the BM for this experimentally artificial means of evoking OHC motion.

Animals↗
PubMed1999

Membrane properties and the excitatory junction potentials in smooth muscle cells of cochlear spiral modiolar artery in guinea pigs.

Blood circulation changes in the inner ear play an important role in many physiological and pathological conditions of hearing function. The spiral modiolar artery (SMA) is the terminal artery to the cochlea. It was surrounded with nerve fibers immunostained by an antibody for tyrosine hydroxylase. By using intracellular recording techniques on the acutely isolated SMA, membrane properties of the smooth muscle cells and the neuromuscular transmission in this preparation were investigated. With minimum tension and normal extracellular K(+) concentration (5 mM), the majority of muscle cells showed a resting potential near -80 mV and an input resistance of about 8 MOmega. V/I plot showed an inward rectification in these cells. Barium (50-500 microM) caused strong depolarization and an increase in input resistance. Transmural electrical stimulation evoked stimulation intensity-dependent depolarizations (2-31 mV) following a short latency ( approximately 20 ms). The evoked potential by a low intensity stimulus was completely blocked by 1 microM tetrodotoxin. The potential and a depolarization induced by norepinephrine (10 microM) was usually partially (40-90%) blocked by alpha-receptor antagonists prazosin and/or idazoxan with concentrations up to 1 microM. Action potentials were observed when the depolarization was more than -40 mV. It is concluded that SMA smooth muscle cells, similar to those in other brain small arteries, highly express inward rectifying potassium channels; the cells receive catecholaminergic innervation, and stimulation of the nerves elicited an excitatory junction potential that is partially mediated by adrenergic receptors.

Animals↗
PubMed1999

Synthesis and characterization of aromatic ring-based cationic lipids for gene delivery in vitro and in vivo.

A new series of cationic lipids has been synthesized for gene delivery using 3,5-dihydroxybenzyl alcohol as the backbone and starting material. Using CMV driven expression system and luciferase gene as a reporter, we demonstrated that the transfection activity of these new lipids when formulated with Tween 80 as co-lipid is comparable to that of DOTAP, one of the most commonly used cationic lipids for transfection. Among the four different cell lines tested including murine melanoma BL-6 cells, human embryonic kidney 293 cells, HepG2 and HeLa cells, the highest transgene expression was seen in 293 cells. Results from in vivo experiments using mice as an animal model show that these cationic lipids preferentially transfect the cells in the lung upon tail vein administration. The cationic lipid, N,N,N-trimethyl-N-[3,5-bis(tetradecyloxy)benzyl] ammonium bromide 4c(di-C14:0) with two 14-hydrocarbon chains exhibits the best transfection activity. These results suggest that these new aromatic ring-based cationic lipids are useful transfection reagents for both in vitro and in vivo gene transfer studies.

Animals↗
PubMed1998

Atmospheric Methane Consumption by Forest Soils and Extracted Bacteria at Different pH Values.

The effect of pH on atmospheric methane (CH4) consumption was studied with slurries of forest soils and with bacteria extracted from the same soils. Soil samples were collected from a mixed hardwood stand in New Hampshire, from jackpine and aspen stands at the BOREAS (Boreal Ecosystem Atmosphere Study) site near Thompson, northern Manitoba, from sites in southern Québec, including a beech stand and a meadow, and from a site in Ontario (cultivated humisol). Consumption of atmospheric CH4 (concentration, approximately 1.8 ppm) occurred at depths of >5 cm in both acidic (pH 4.5 to 5.2) and alkaline (pH 7.2 to 7.8) soils. In slurries of acidic soils, maximum activity occurred at different pH values (pH 4.0 to 6.5). Bacteria extracted from these soils by high-speed blending and density gradient centrifugation showed pH responses different from the pH responses of the slurries. In all cases, these bacteria had a methanotrophy pH optimum of 5.8 and exhibited no activity at pH 6.8 to 7.0, the pH optimum range for known methanotrophs. This difference in pH responses could be useful in modifying media currently used for isolation of these organisms. Methanotrophic activity was induced in previously non-CH4-consuming soils by preincubation with 5% (vol/vol) CH4 (50,000 µl of CH4 per liter) or by liquid enrichment with 20% CH4. The bacteria showed pH responses typical of known methanotrophs and not typical of preexisting consumers of ambient CH4. Furthermore, methanotrophs induced by high CH4 levels were more readily extracted from soil than preexisting ambient CH4 consumers were. In the alkaline soils, preexisting activity either was destroyed or resisted extraction by the procedure used. The results support the hypothesis that consumers of ambient CH4 in soils are physiologically distinct from the known methanotrophs.

Journal Article↗
PubMed1998

Modification of development by the CFTR gene in utero.

The in utero infection of rats at 16-17 days gestation with a recombinant adenovirus carrying the human cystic fibrosis transmembrane conductance regulator (cftr) gene resulted in altered lung development and morphology. These structural alterations prompted an evaluation of concurrent functional changes in the cftr-treated lung. CFTR protein could be detected in treated lungs for up to 30 days postinfection, although it was not detected in the intestines at this time. Increased levels of secreted glycoconjugates and lipids were found in lungs treated in utero with human cftr and large vacuoles containing glycoconjugates were detected within cells of the intestines. The scope and durability of these changes suggested that in utero cftr treatment influenced the activity of secretory cells in the developing lung. Altered secretory products in the lungs of cystic fibrosis patients are thought to be associated with increased susceptibility to Pseudomonas aeruginosa infection. We challenged 3-month-old rats (treated in utero with the human cftr gene) with a lethal, intratrachial dose of this bacteria. Rats treated with cftr exhibited enhanced resistance to Pseudomonas infection when compared to controls. These animals displayed little or no associated inflammatory response. No evidence of the adenovirus transgene was detectable at the time of P. aeruginosa inoculation, indicating that continuous ectopic expression of hcftr was not required for enhanced protection. These data demonstrate that in utero, cftr expression influenced the development and function of cells involved in the primary host defense against bacterial infection in the lung.

Adenoviridae↗
PubMed1998

Acoustical modulation of electrically evoked otoacoustic emission in intact gerbil cochlea.

In order to study the interaction between mechanical-electrical and electrical-mechanical transductions of outer hair cells (OHCs) in vivo, we observed the acoustically induced changes in the electrically evoked otoacoustic emission (EEOAE). One pole of a bipolar electrode was placed in the round window niche and the other pole on the surface of the first cochlear turn in the gerbil. A microphone and a speaker were used to monitor the EEOAE and to deliver an acoustical tone, respectively. It was found that a high sound level acoustical tone enhanced the EEOAE fine structure at frequencies below the acoustical frequency, and suppressed the overall level of the EEOAE at frequencies above the acoustical frequency. In addition, the EEOAE at frequencies approximately one half octave lower than the acoustical frequencies were relatively more enhanced or showed relatively less suppression than at other frequencies. The amplitudes of these changes had a positive relationship with acoustical tone levels. Furosemide eliminated the acoustically caused EEOAE change indicating that the acoustically caused change in the EEOAE is a phenomenon of the normal cochlea. One possible mechanism for the results is that the electrically and acoustically evoked basilar membrane (BM) vibrations interact at the EEOAE generation site and change the local mechanical and electrical properties. The second possible mechanism is that the acoustical stimulus creates an impedance discontinuity at its characteristic frequency location leading to a change in the reflected electrically evoked traveling wave, which may enhance or suppress the EEOAE by the vector summation of two waves.

Acoustic Stimulation↗
PubMed1998

Comparative health risk assessment of nuclear power and coal power in China.

The public health risk of ionising radiation released from the coal-fired energy chain, 20 deaths (GW a)(-1), is about 18 times that of the nuclear energy chain, 1.1 deaths (GW a)(-1), in China. The main contributors to the fatality risk for the former are the public dose caused by the use of coal ash and the occupational exposure caused by radon and its progeny in coal mines. The total health risk (but excluding low probability/high consequence accidents) of the coal-fired energy chain, 57.1 deaths (GW a)(-1), is about 12 times of that of the nuclear energy chain, 4.6 deaths (GW a)(-1). The health risk of coal-fired energy chain could be significantly reduced if technique and management were improved. Even then the risk of the coal-fired energy chain is about 4.4 times that of the nuclear energy chain.

China↗
PubMed1998

Age-related changes in cochlear blood flow response to occlusion of anterior inferior cerebellar artery in mice.

Previous studies suggest that autoregulation of cochlear blood flow (CBF) may be impaired by aging. In this study, we quantified the capacity of CBF autoregulation in young adult (6-month-old) and aged (21-month-old) CBA mice, to examine the effect of aging on CBF autoregulation. The technique of anterior inferior cerebellar artery (AICA) occlusion was employed to manipulate cochlear perfusion pressure. The CBF was measured by laser Doppler flowmetry during intermittent occlusion of the AICA with a microvascular clamp, which causes an initial decrease in CBF. The autoregulation of CBF was evaluated by quantifying the CBF increase (compensatory dilatory response in the cochlear vessels) during AICA occlusion. Our results demonstrated that autoregulation of CBF was significantly reduced and that collateral vascular function supplying CBF was significantly lower in the aged group. These findings suggest that the aged ear has less capacity to maintain stable blood flow and thus may be more vulnerable to stress factors that affect cochlear function.

Age Factors↗
PubMed1997

The tonic sympathetic input to the cochlear vasculature in guinea pig.

Vascular tones is an essential component in maintaining steady regional blood flow and dynamic responsiveness of a vascular bed. Sympathetic innervation can contribute to vascular tone. Although certain studies have reported evoked changes in cochlear blood flow (CBF) with activation of the sympathetic fibers to the cochlear vasculature, other studies have failed to show evidence of sympathetic contribution to CBF regulation when the cervical sympathetic fibers were unilaterally sectioned. We hypothesized that the bilateral 'sympathectomy of the stellate ganglia' would remove sufficient sympathetic input to the cochlea to yield a change in CBF resting level. To test this hypothesis a new technique was used to expose the stellate ganglia (SG) bilaterally and induce a chemical sympathectomy. We observed that unilateral SG blockade with 2 microliters of 4 mM lidocaine hydrochloride on either side produced a 5-10% increase in CBF, which recovered to baseline during the following 2 min. A subsequent blockade of the contralateral SG produced a rapid 25-35% increase, which then recovered partially during the following 3-4 min, remaining 5-15% above the baseline over a 20 min measurement period. Superior cervical ganglion transection did not affect CBF. Our results provide evidence for the existence of a tonic sympathetic component in the control of vascular tone in guinea pig cochlea. This neural effect is derived bilaterally from SG. This result is consistent with previous anatomical studies showing the bilateral innervation of the cochlea by the SG sympathetic fibers and with previous physiological studies on the bilaterality of evoked changes in CBF due to electric stimulation of SG.

Anesthetics, Local↗
PubMed1997

ATP-induced cochlear blood flow changes involve the nitric oxide pathway.

Although control mechanisms of cochlear blood flow (CBF) have been intensively studied since laser Doppler flowmetry was introduced for CBF measurement in animals and humans, the role of adenosine 5'-triphosphate (ATP) in CBF regulation is not known. Since ATP is a potent vasoactive agent in other organs, the aim of this study is to examine ATP-induced changes in CBF and to test whether the nitric oxide pathway is involved in ATP-induced CBF changes. The anterior inferior cerebellar artery (AICA) of anesthetized pigmented guinea pigs was exposed, and ATP was perfused into the AICA. For CBF measurement, the bulla was opened and the 0.7 mm laser probe of a Perimed PF2B flowmeter was positioned on the basal turn of the cochlea. AICA perfusion of an ATP solution caused dose-dependent transient CBF increases. The maximum CBF increase induced was 220% of the baseline. In some animals, CBF showed a dual effect; a transient decrease followed by a longer-lasting increase. The perfusions of sodium nitroprusside (SNP) also resulted in dose-dependent CBF changes. The intravenous application of N(omega)-nitro-L-arginine methyl ester (L-NAME) significantly attenuated ATP-induced CBF increases, and enhanced ATP-induced decreases, but did not affect SNP-induced CBF changes. The ATP-induced CBF responses indicate that ATP plays a role in CBF regulation. The biphasic characteristic of the ATP-induced CBF change suggests the involvement of both P2x- and P2y-subtype purinoceptors. That L-NAME caused attenuation of the ATP-induced CBF increase implies that the ATP-induced CBF increase is mediated by the release of endothelium-derived relaxing factor, nitric oxide, following activation of endothelial P2y-purinoceptors in the cochlear vascular bed and/or cochlear supplying vessels.

Adenosine Triphosphate↗
PubMed1997

Basilar membrane velocity noise.

Basilar membrane (BM) noise, measured as a velocity signal under the quiet acoustic condition, was investigated in the guinea pig. The cochleas of anesthetized young healthy guinea pigs were surgically exposed and a hole was made on the lateral wall of the scala tympani of the first cochlear turn for visualization of the BM and measurement of the BM velocity with a laser interferometer. The amplitude and frequency of the BM velocity noise were analyzed by a spectrum analyzer under different conditions. The spectrum of the BM velocity noise was a band limited function with a peak velocity at the topographic best frequency of the measured location on the BM. The peak velocity ranged to about 8 microm/s and depended on the physiological condition of the cochlea. Saline blockage of the external auditory canal or the middle ear did not change the BM noise. BM noise was much smaller, or was not evident, when the cochlear sensitivity decreased. The suppression tuning curve of the BM velocity noise indicates that the maximum suppression caused by an acoustic pure tone occurred at the best frequency location. A low sound level wide band acoustic noise given to the external ear canal produced a spectrum function having the same frequency and amplitude response as the BM noise. Electrical stimulation of the crossed olivocochlear bundle significantly depresses the BM velocity noise. These data demonstrate that the BM noise is a representation of internal rather than external noise. The amplitude and frequency of the BM noise reflect the usual cochlear sensitivity and frequency selectivity. Since the organ of Corti in the sensitive cochlea is a highly sensitive and tuned mechanical system, the internal (to the animal) noise responsible for the BM noise may originate from mechanical vibrations remote from the cochlea and propagated to the ear, or may be caused by Brownian motion of cellular structures in the cochlea.

Acoustic Stimulation↗